When a hearing instrument is inserted in the ear canal, the canal may be “occluded,” i.e., blocked. This may cause the user to experience a hollow sound when speaking, a phenomenon called the “occlusion effect.” One solution is to provide a vent that allows the sound pressure that develops in the ear canal to escape.
The occlusion effect may also be addressed by using the resulting sound to electronically cancel or minimize its effect. An ear-canal microphone captures that sound in the occluded ear and the signal is provided to circuitry in the receiver that uses the ear-canal microphone signal to cancel the sound. (See, e.g., U.S. Pat. No. 6,937,738, issued on Aug. 30, 2005, for a “Digital Hearing Aid System,” incorporated here by reference.)